At least 320 Shi'ites have been killed in targeted attacks this year across Pakistan, including more than 100 in south-western Baluchistan province, the majority from the Hazara community, the US-based group it said in a statement.

"Deadly attacks on Shia (Shi'ite) communities across Pakistan are escalating," Mr Brad Adams, Asia director at Human Rights Watch, said in the same statement.

"The government's persistent failure to apprehend attackers or prosecute the extremist groups organising the attacks suggests that it is indifferent to this carnage," Mr Adams said.